The present invention relates to a porous sintered body and a method of manufacturing such a porous sintered body, and more particularly to a porous sintered body for use in a filter which deodorizes a liquid or a gas or removes contaminating substances, or for use as a polarized electrode in a capacitor, and a method of manufacturing such a porous sintered body.
Recently, filters made of nonwoven metal fabric are used for deodorizing liquids or gases or for removing contaminating substances. Such a nonwoven metal fabric filter typically comprises a compressed lamination of metal fibers such as slender fibers of stainless steel, the compressed lamination being heated to fuse the metal fibers. Since the metal fibers are not subject to corrosion, the filter is not corroded even when it is exposed to air or liquids for a long period of time.
Filters made of nonwoven fibrous activated carbon fabric are also used to deodorize liquids. The activated carbon fibers cannot be bonded together in regions where they are held in contact with each other. Therefore, the filters made of nonwoven fibrous activated carbon fabric are kept under pressure at all times by some process, so that the filters are compressed during use.
There are also employed compressed sintered filters which are made of bonded spherical particles of metal or activated carbon.
Since the nonwoven fabric is pressurized and sintered, the nonwoven fabric filters have a porosity of 60% or greater, and also have uneven pores between the metal fibers.
The filters made of fibrous activated carbon require some means for compressing themselves at all during usage, and hence are complex in structure. The filters of this type are also disadvantageous in that the pores between the fibers are uneven or irregular.
The compressed sintered filters are fabricated by compressing and sintering metal or activated carbon particles which are mixed with a particle binder. After the filters are sintered, the particle binder is removed. If the particle binder is not thoroughly removed, then the fabricated filter has poor filter characteristics.
The conventional filters of the types referred to above are further disadvantageous in that the pores between the fibers or particles are not of uniform size. If a compressed sintered filter were manufactured using fibers or particles having diameters smaller than several .mu.m, the fibers or particles would be melted, substantially entirely clogging the pores. Therefore, fibers or particles of very small diameters cannot be employed. The compressed sintered filters are thus not suitable for use in removing germs which are about 10 .mu.m in size, such as colitis bacteria.
Porous sintered bodies made up of fibers or particles of activated carbon have a small space factor per unit volume and a small surface area per unit volume since the size of the fibers or the diameter of the particles is large. If a polarized electrode of an electric double layer capacitor is constructed of a porous sintered body, then an electric double layer capacitor of high capacitance cannot be obtained. Furthermore, if the particle binder is not sufficiently removed then the manufactured electric double layer capacitor fails to achieve desired characteristics sufficiently.